<template>
  <div class="pagination">
    <button @click="changePageNo(pageNo -1)" :disabled="pageNo === 1">上一页</button>
    <button  @click="changePageNo(1)" v-show="startend.start !== 1">1</button>
    <span v-show="startend.start > 2">···</span>

    <!-- <button>{{ startend.start }}</button>
    <button>???</button>
    <button class="active">{{ pageNo }}</button>
    <button>???</button>
    <button>{{ startend.end }}</button> -->

    <!-- 循环遍历展示连续分页按钮 -->
    <button 
      @click="changePageNo( startend.start + index)"
      :class="{active:pageNo == index+startend.start}" 
      v-for="(n,index) in (startend.end - startend.start +1)" 
      :key="index">
      {{ startend.start + index }}
    </button>

    <span v-show="startend.end < totalPage-1">···</span>
    <button @click="changePageNo( totalPage  )" v-show="startend.end !== totalPage">{{ totalPage }}</button>
    <button @click="changePageNo( pageNo + 1)" :disabled="pageNo === totalPage">下一页</button>

    <span>共 {{ total }} 条</span>
  </div>
</template>

<script>
export default {
  name: "Pagination",
  props: {
    // 总数
    total: {
      type: Number,
      // required: true,
    },
    // 每页展示数量
    pageSize: {
      type: Number,
      required: true,
    },
    // 页码
    pageNo: {
      type: Number,
      required: true,
    },
    // 连续页码
    continues: {
      type: Number,
      default:5
    },
    // 接收父组件传递的方法
    changePageNo:{
      type:Function,
      required:true
    }
  },
  computed: {
    // 计算最大页码
    totalPage() {
      return Math.ceil(this.total / this.pageSize);
    },
    // 计算连续分页的页码
    startend() {
      let { pageNo, continues, totalPage } = this;
      let start = 0;
      let end = 0;
      // 判断连续页码是否大于所有页码
      if (continues > totalPage) {
        start = 1;
        end = totalPage;
      } else {
        start = pageNo - (continues - 1) / 2;
        end = pageNo + (continues - 1) / 2;
        // 判断当连续分页小于最大页码数  当前页码为2展示情况
        if (start < 1) {
          start = 1;
          end = continues;
        }
        // 判断当连续分页小于最大页码数  当前页码为end溢出展示情况
        if (end > totalPage) {
          start = totalPage - continues + 1
          end = totalPage;
        }
      }

      return {
        start,
        end,
      };
    },
  },
};
</script>

<style lang="less" scoped>
.pagination {
  text-align: center;

  button {
    margin: 0 5px;
    background-color: #f4f4f5;
    color: gray;
    outline: none;
    border-radius: 2px;
    padding: 0 4px;
    vertical-align: top;
    display: inline-block;
    font-size: 13px;
    min-width: 35.5px;
    height: 28px;
    line-height: 28px;
    cursor: pointer;
    box-sizing: border-box;
    text-align: center;
    border: 0;

    &[disabled] {
      color: #c0c4cc;
      cursor: not-allowed;
    }

    &.active {
      cursor: not-allowed;
      background-color: #c81623;
      color: #fff;
    }
  }

  span {
    display: inline-block;
    line-height: 28px;
    font-size: 14px;
    color: gray;
    vertical-align: middle;
  }
}
</style>